1. Field of the Invention The invention relates to an injector for a common rail injection system of an internal combustion engine.
2. Prior Art
Common rail injection systems have a plurality of injectors, which under the control of an electronic motor controller are supplied with fuel by a high-pressure pump from a central high-pressure reservoir known as a common rail and inject the fuel into the combustion chambers of the engine.
From German Patent Disclosure DE 100 20 870 A1, a common rail injector is already known whose injector housing contains a valve element that is inserted into a stepped bore in the injector housing and is sealed from the injector housing by a soft sealing ring, which serves as a seal between a high-pressure region and a low-pressure region of the injector. The sealing ring is inserted into an annular chamber above an annular shoulder of the stepped bore and is braced against the annular shoulder. To prevent the sealing ring from being pressed or extruded into a narrow annular gap, located below the annular shoulder, between the valve element and the injector housing as a result of the varying fuel pressures of up to 1900 bar that prevail in the high-pressure region of above the sealing ring, a metal support ring is disposed between the sealing ring and the annular shoulder. Since at the aforementioned pressures complete tightness of the sealing ring cannot be assured, the support ring, on its underside toward the annular shoulder, is provided with a total of four shallow leak fuel or relief grooves, which furnish a defined lack of tightness between the support ring and the injector housing so as to carry away a leak fuel flow moving past the sealing ring and thus prevent the buildup of a pressure cushion below the sealing ring, which could lead to an unwanted axial displacement of the sealing ring.
Since in injectors for common rail injection systems currently being mass produced by the assignee of this invention, the support ring furthermore rests sealingly with its outer circumferential edge against the adjacent inner wall of the stepped bore, it furthermore has, adjacent to one another in the axial direction on each relief groove, a crescent-shaped indentation recessed out of its outer circumferential edge, which is meant to allow the leak fuel flow to pass between the outer circumferential edge of the support ring and the adjacent inner wall of the stepped bore into the relief grooves. With such an arrangement, however, an unwanted extrusion of the sealing ring material through the recesses and the relief grooves could occur, so that the sealing function of the sealing ring could no longer be assured and consequently failure of the entire injection system could be brought about.